It is not unusual to find multiple diverse instances wherein larger molecule liquids have been mixed with water and/or other smaller molecule liquids. For example, bilge water typically comprises a mixture of petroleum oil and/or other organic solvents with water, as does typical liquid waste collections from automotive repair and wash facilities, machine shops, metal stamping plants, and generally any number of industrial or repair processes wherein liquids such as water and organic materials such as oils, solvents, coolants and the like are commingled in use or collection.
There has been an increasing need for means to separate larger molecule liquids, water and/or solids mixtures so that clean water can be returned to the environment while the larger molecule liquids and/or solids can be recovered and recycled.
One device which is generally commercially available for the separation of such mixtures is an ultrafiltration device as disclosed in U.S. Pat. No. 5,069,780. In such ultra-filtration device a fluid containing mixture is directed, under pressure, to an ultra-filtration membrane. The ultra-filtration membrane preferably comprises microscopic hydrophilic pores which will allow water to pass through the membrane but resist the passage of larger sized organics such as oil, solvents and/or solids molecules. Such selective activity is a function of the membrane, achieved through a combination of membrane characteristics including pore size, liquid contact angle and liquid surface tension. The membrane is typically arranged in a cross flow configuration wherein a feed from a water/oil mixture flows across the ultrafiltration membrane at a pressure which allows water in the mixture to permeate the membrane which resisting the flow of larger molecules through the membrane.
The defining parameters of ultrafiltration devices of the type above described are generally significantly affected by the efficiency of the membrane assembly and the convenience of maintaining such efficiency. Thus, the volume of liquid flow through the device, the power efficiency of the pump enabling pressurized flow through the device and the quality of the ultra-filtration attained depends primarily upon the filtering capability of the membrane, but the ability to maintain an efficient flow of fluid along the membrane and maintain the membrane from fouling or otherwise clogging to reduce its efficiency are generally factors defined by the membrane assembly.
Maintaining the efficient flow of fluids across the membrane and reducing the tendency of the membrane from clogging can require extensive and complex periodic disassembly of the device for routine cleaning and/or maintenance and as a result such units have not enjoyed a level of commercial utility that might otherwise be expected.
It is an object of the present invention to provide a membrane assembly, particularly useful for ultrafiltration of fluids, which is convenient to connect into ultrafiltration devices, efficient in directing fluid flow across the membrane, is resistant to membrane clogging and can be easily cleaned and/or replaced in a complex ultra-filtration device. These and other objects will become apparent from the following description of the invention.